Halftone matrix for use with fine features

Abstract

A method in described in which image data to be printed and a halftone matrix are provided. The halftone matrix comprises rows having randomized values within alternating ranges of values. The halftone matrix is applied to the image data to generate a plurality of halftone patterns.

What is claimed is: 
     
       1. A method comprising:
 providing image data to be printed; 
 applying a halftone matrix to the image data to generate a plurality of halftone patterns; 
 
       wherein the halftone matrix comprises rows of elements having a sequence of ranges of values where each element is randomized within a corresponding range of values. 
     
     
       2. A method as claimed in  claim 1 , wherein the image data comprises a Neugebauer Primary area coverage (NPac) vector, and applying the halftone matrix to the image data comprises assigning a Neugebauer Primary (NP) to each pixel of the halftone pattern according to the NPac vector and the value of the corresponding element of the halftone matrix. 
     
     
       3. A method as claimed in  claim 1 , wherein the image data comprises an Ink vector, and applying the halftone matrix to the image data comprises assigning a colorant to pixels of the halftone pattern according to the proportion of the colorant in the Ink vector and the value of the corresponding element of the halftone matrix. 
     
     
       4. A method as claimed in  claim 1 , wherein the sequence of ranges varies regularly or randomly within each row and between rows. 
     
     
       5. A method as claimed in  claim 2 , wherein values are allocated to each NP according to the coverage area of the NP in the NPac vector. 
     
     
       6. A method according to  claim 5 , wherein the values allocated to each NP are based on a cumulative coverage area of the NPs in the NPac vector. 
     
     
       7. A method according to  claim 6 , wherein the accumulation of NP's is based on tone. 
     
     
       8. A method according to  claim 1 , wherein the halftone matrix is a PARAWACS matrix. 
     
     
       9. A method as claimed in  claim 1 , wherein each row of the halftone matrix has a uniform distribution of values and the halftone matrix has an equal frequency of each value. 
     
     
       10. A method as claimed in  claim 1 , wherein the halftone matrix comprises one or more of the following: two alternating ranges; alternating ranges arranged in a repeating order; alternating ranges arranged in a random order. 
     
     
       11. A method as claimed in  claim 1 , wherein the alternating ranges of a row are arranged differently to the alternating ranges of an adjacent row. 
     
     
       12. A method as claimed in  claim 11 , wherein the alternating ranges of each row are arranged in a repeating order and the repeating order of a said row is offset compared with an adjacent row. 
     
     
       13. A method as claimed in  claim 12 , wherein the alternating ranges of adjacent rows are arranged to form a zig-zag pattern of common alternating ranges. 
     
     
       14. A printing device comprising:
 a printhead assembly; 
 a processor; and 
 a storage medium storing a halftone matrix and instructions for execution by the processor; 
 wherein the halftone matrix comprises rows of elements having a sequence of ranges of values where each element is randomized within a corresponding ranges of values; and 
 wherein the instructions, when executed by the processor, cause the processor to: 
 receive image data; 
 apply the halftone matrix to the image data; and 
 print the halftone patterns using the printhead assembly. 
 
     
     
       15. A non-transitory computer-readable storage medium comprising a set of computer-readable instructions that, when executed by a processor, cause the processor to:
 generate a halftone matrix comprises rows of elements having a sequence of ranges of values where each element is randomized within a corresponding ranges of values; and 
 applying the halftone matrix to image data to generate a plurality of halftone patterns.